SCALP HAIR LENGTH 369 Table II Percentage of Different Populations by Age* Age group USA Developed world** Entire world Under 15 21 18 32 15 to 60 63 63 58 60 and over 16 19 10 * Calculated from data of the United Nations Statistics Division (2). ** Consists of 43 countries including the USA, most of Europe, Japan, the Russian Federation and adjoining countries, and Australia, and represents 20% of the world's population. III, Figure 1) to anatomical measurements so that we might estimate the actual hair lengths of these populations. Some of the data from our former paper is provided in Table III along with calculations to estimate the percentages of people with hair lengths between the limits of every two anatomical sites. To relate the anatomical positions to actual hair lengths, six people were measured (three females and three males), ranging in height from 158 cm to 191 cm (5'2" to 6'3") (see Table IV). Measurements were actually taken with a tape measure made in the USA based on the English system (inches) and then converted to centimeters by multiplying by 2.54. Two sites were taken on the head to measure from, one near the frontal area, indicated as A, and the other representing the crown area, marked B in Figure 1. The distance from the frontal area to the crown averaged 12.7 cm. Measurements made from the crown to the anatomical positions are listed in Figure 1, and these were converted to hair lengths in centimeters (see Table IV). The data from Table IV allow estimates from both the crown area and the frontal area to the anatomical sites. Total ranges and midpoints are listed for each anatomical site in Table V. For the hair-length calculations in this paper, the approximate midpoints for the ana- tomical sites were used. These actually represent the free-hanging lengths rather than the actual lengths. The actual lengths of the hair when pulled taut will always be longer than the free-hanging lengths because of hair curvature (see footnote in Table IV). The midpoints from the ranges of these measurements (Table V) were then used with the data from the theme parks, i.e., the percentage of persons between the anatomical sites (Table III) along with additional data for subsequent treatment and conclusions. Table III Hair Length and the Percentage of Persons From Study of 24,300 Persons (11)* Anatomical position % At site or longer % Between sites** Shoulder-length or longer Between shoulder and lower shoulder blade Lower shoulder blade or longer Between lower shoulder blade and waist Waist-length or longer Between waist and buttocks Buttocks-length 13.20 10.77 2.43 2.11 0.317 0.301 0.0165 * Males plus females ** The actual data are percentages at the site or longer. Subtracting the numbers for the longer lengths permits calculation of the percentages between sites.

370 JOURNAL OF COSMETIC SCIENCE A D APPROXIMATE HAIRLENGTHS (CM) From B From A Midpoint 12.7 to 17.7 22.9 to27.9 E 25 to 33 38 to 46 35.5 F 46 to 51 58 to 64 55 G 61 to 76 74 to 89 75 H 89 to 107 102 to 119 104 I 117 to 142 130 to 155 136 j 147 to 180 160 to 193 170 A = Frontal B = Crown C = Occipital [] = Chin E = Shoulder, F = Lower shoulder blade G = Waist H = Buttocks I = Knee and J = Ankle. The distances from Ato B and B to C are 10.2 and 12.7 cm plus or minus 1. Figure 1. Measurements of anatomical positions relating to free-hanging hair lengths. CALCULATIONS (ESTIMATES) FOR THE USA AND LARGER POPULATIONS Four data points from the theme park studies expressed as hair lengths based on the anatomical site measurements (Table V--Approximate midpoints) were plotted against the natural logarithm of the percentage of the population between sites (Table III), providing the graph in Figure 2. This represents the use of 3,208 data points rather than the total of 24,300 from our theme park studies. The equation representing this straight